Catalyst



was June 24,1941 h 2 245 2 UNITED STATES PATENT OFFICE CATALYSTLlewellyn Heard, Hammond, Ind., and Alex G. Oblad, Chicago, 111.,assignors to Standard Oil Company, Chicago, 111., a corporation ofIndiana No Drawing. Application November 16, 1938,

Serial No. 240,642

2 Claims. (Cl. 252- 230) This invention relates to catalysts and morethat it possesses considerable dehydrogenating particularly to catalystshaving a metal chromite activity in itself, and possesses all thecharacteras a support. istics necessary for a suitable catalyst support.

In the catalytic" conversion of hydrocarbons, These metal chromites maybe prepared as folwhich includes such processes as cracking, .3 lows: Anaqueous solution of a suitable salt, such polymerization, hydrogenation,dehydrc'igenation, as for example magnesium chloride or magnesiumalltylation, etc., a great variety of compounds nitrate, is mixed withammonium chromate or have been used In many, and in fact in most,dichromate, preferably in approximately stoichioinstances it has been,found desirable to support metric proportions, although an excess ofthe the most active catalytic material on a sub chromium compound may beused, and the solustance which is much less active, or even inert. tionallowed to stand until well-defined crystals The reason for this may bebased on the physioi? the hydrated metal ammonium chromate calcharacteristics of the active catalytic mateform. The crystals are thenfiltered off, washed rial which is often of such nature that it does notand dried, and heated until they give off water lend itself to theformation of the proper catalyst and ammonia and are substantiallycompletely form; it may be desirable to dilute! the catalyticdecomposed. The temperature used is not critimaterial in order to reduceits activity; or it cal but in general should be in the neighborhood maybe desirable to supply additional surface for of red heat. This methodof preparation is dei better contact between the material undergoingscribed in the copending application of one of conversion and thecatalyst. The usual supports 20 us, Llewellyn Heard, Serial No. 180,302,filed Defor such catalysts are such materials as pumice, cember 17, 1937now U. S. Patent No. 2,205,140.

clays, kieselguhr, fire brick,.etc., which are com- A microscopicexamination of magnesium paratively inert, or gels such as silica gel orchromite prepared in this manner reveals it to chromium oxide gel, whichmay modify the catabe of highly porous nature and it has been foundlytic activity of the primary catalyst. Each of to withstandtemperatures up to 1000 F. and 1 these materials has certain advantagesand dis higher without undergoing any transition of the i advantages;for example, the inert materials will crystal state. Moreover, thecrystals are usually supply additional contact surface and aid in the ofa size and shape suitable for use in the catalytic formation ofcatalysts of suitable size, shape and conversion of hydrocarbons.However, if desirphysical stability but will not influence to any able,they may be crushed and screened to pregreat' extent the catalyticactivity of the primary determined size or may be pelleted or otherwisecatalyst. The gels, on the other hand, while in shaped, either before orafter the deposition of many cases offering suitable modifications ofthe active catalytic material. Metal chromltes the catalytic reaction,are quite subject to disprepared in any other manner, for instance byintegration and inactivation at the high temthe thermal decomposition ofammonio metal peratures necessary for the catalytic conversion ammoniumchromate or ammonio metal chroprocess. mates, are equally suitableproviding they pos- It is an object of our invention to provide new sessthe refractivity and porosity exhibited by the and improved catalystswhich are of a refractory metal chromites prepared in accordance withthe nature and characterized by large surface area. 40 abovedescription. Another object of our invention is to provide a In theevent that the crystalline metal chrosupport for catalytic agents whichalso modifies mites are too finely divided, when originally beneficiallythe catalytic effect of the catalytic formed, to be suitable as acatalyst support, they agent. It is a further object of our inventioncan be ground to a powder in a ball-mill or simto provide an improvedand a highly eilicient catilar pulverizing means, the powder formed intoalyst for the dehydrogenation of hydrocarbon a paste with water, and thepaste dried, prefermaterials. Further objects will become apparably in athin sheet. The dried product can now ent from a reading of thefollowing more detailed be crushed and screened to the proper size, anddescription of our invention. will possess the refractivity and porosityneces- We have found that the metal chromites which 50 sary for asuitable catalyst support. Metal chroare prepared by the thermaldecomposition of mites which canbetreated in this manner includecrystalline hydrated metal ammonium chrothe chromites of copper,aluminum, zinc, cobalt, mates are particularly suitable as catalystsupmanganese, uranium, sodium, calcium, barium. ports. Of these metalchromites we prefer to and strontium. When preparingcatalyst supusemagnesium chromite since we have found ports in this manner, it ispossible to use a solution of the active catalytic material as themedium for forming the paste, in which case further impregnation of thesupport is unnecessary.

The active catalytic material may be deposited upon the metal chromitein a number of different ways; for example, the chromite may be immersedin a solution of the active catalyst material and because of the porous,capillary nature of the chromite, the salt solution is adsorbed. Theexcess can then be poured ofl and the catalyst dried.

If it is desirable to incorporate metals or metal oxides on the catalystsupport this may be accomplished by impregnating the catalyst with anaqueous solution of a metal salt subject to ready thermal decompositionto the oxide of the metal or to the metal itself. After the salt-impreg-Example I.-A catalyst was prepared as follows: Magnesium chromiteprepared by the decomposition of magnesium ammonium chromate hexahydratewas immersed in a 3% solution of platinum chloride, the excess liquordecanted, the impregnated chromiteoven-dried, and then reduced for onehour with hydrogen, while the temperature was elevated to 800 F. Asweetened octane cut was passed over this catalyst at a temperature ofapproximately 900 F. and a space velocity of approximately 0.8liquid/volume catanated chromite is dried it is subjected to suitableheat in the presence of hydrogen or a hydrocarbon, if desired, with thereduction of the salt to a suitable oxide or metal completely and finelydeposited throughout the support.

' It is also possible to prepare active catalysts by the deposition ofcarbonyls on the magnesium chromite with the-subsequent decomposition ofthe carbonyl to leave the metal deposited on the support. Volatile metalcarbonyls' may be incorporated under pressure while the nonvolatilecarbonyls may be adsorbed in the liquid phase. Double metal carbonylsare equally applicable.

All of these methods of incorporating active catalytic materials on asupport have been known for some time. and other methods of applyingsuitable catalysts will occur readily to one skilled in the art.

We have found that catalysts in which a metal chromite is used as asupport are particularly eflicacious in the dehydrogenation ofhydrocar-. bons. Because of their highly refractory and highly porousnature they are equally applicable to other catalytic processes where alarge surface area is of advantage and where the temperatures employedrequire the use of a heat-resistant material.

Our invention will be better understood from the following specificexamples which demon strate the effectiveness of our catalyst in thedehydrogenation of hydrocarbons.

lyst space/hour. The refractive index increased from 1.4194 to 1.4281and the eiiiux gas contained approximately 85% evolved at a rate ofapproximately 4800 cc. per hour. The catalyst was substantiallycompletely regenerated by the simple expedient of air blowme andreducing.

- Example II.-Magnesium chromite prepared as above was immersed first ina saturated solution .of nickel formate, followed by immersion in a 3.0%solution of platinum chloride. .The'impregnated chromite was dried atapproximately 180- F; and reduced for one hourwith hydrogen, while thetemperature was elevated to 900 F. A

. sour petroleum octane stock consisting substan tially of saturatedhydrocarbons Was passed over this catalyst at atemperature' ofapprommately 900 F., at atmospheric pressure, and a space velocity ofapproximately 1.0 liquid/volume catalyst space/hour. The refractiveindex increased from 1.419% to 1.4301 and'the product containedapproximately 8.0% ,by weight of'ol'efins. The

eiilux gas contained approximately 85% hydrogen, the gas being evolvedat a rate of approximately @760 cc. per hour.

Although we have described our invention in relation to certain specificembodiments thereof, we do not intend to be limited thereby exceptinsofar as is set forth in the appended claims.

We claim:

1. As a hydrocarbon conversion catalyst, platinum supported on magnesiumchromite.

2. As a hydrocarbon conversion catalyst, nickel and platinum supportedon magnesium chromite.

LLEWELLYN HEARD. ALEX G. OBLAD.

hydrogen, the gas being-

